The amount of time kids spend in front of screens -- on computers, tablets and smart phones -- also plays a role, as do parenting styles in the home.

All of it can contribute to a child’s academic success, sleep problems, emotional stability, focus, and behaviors commonly linked to ADHD, a new study shows.

In the Learning Habit Study, researchers used an online survey to gather data from families with kids in kindergarten through 12th grade to look at connections between family time, parenting styles, and screen time with a range of child behaviors.

Among their findings:

Family time, including family dinners, playing board games, and attending religious services together, resulted in less screen time for kids and helped boost their social and emotional coping skills, have better focus, and do better academically.

Traditional parenting styles -- those that discipline when kids misbehave or underperform -- had a negative impact on academic achievement. It left kids with more social and emotional challenges, focus and sleep problems, and a 10% higher rate of symptoms commonly linked to ADHD.

Parenting styles that rely on positive reinforcement and are firm, but supportive, had the opposite effect. They contributed overall to higher rates of healthy outcomes, including a 3% lower rate of children with ADHD symptoms.

The amount of screen time a child has each day can quickly add up to have a bad effect on behavior, emotions, and academics, even though it can increase the amount of time some children spend doing homework. Researchers found grades began to decline steadily after just 45 minutes of screen time and dropped even more significantly after 2 hours. More screen time led to greater sleeping problems, too.

The study will be published Tuesday in the Journal of Family Psychology.